"Comet Hale-Bopp Approaches: The Importance of Comets to
Life on Earth" will be the theme for a free public lecture to be
held at 7 p.m., Thursday, March 20, in JPL's von Kármán
Auditorium, 4800 Oak Grove Drive, Pasadena. Seating is on a
first-come, first-served basis.

Comets, composed of ice and dust, are believed to be the
remnants of the birth of the solar system. Their primordial
material may lend clues in learning more about the origin and
evolution of the planets. Originating in a region from beyond the
orbit of Pluto, comets can have orbits taking several thousand
years to complete.

As comets draw closer to the Sun, their surface material
begins to heat up and vaporize, creating the long tail of dust
and gas that makes a comet visible to observers on Earth. Comet
Hale-Bopp, named after co-discoverers Alan Hale and Thomas Bopp,
is returning to orbit the Sun after 4,200 years. The comet is
currently visible at dusk and just before dawn in the Northern
Hemisphere, and will make its closest approach to Earth of about
122 million miles on March 22.

Several NASA missions are planned to further study the
nature of comets. Stardust, scheduled for launch in 1999, will
capture ejected materials from Comet Wild 2 in 2004 and return
those samples to Earth in 2006. New Millennium Deep Space One,
scheduled for launch in 1998, will fly by the asteroid named
McAuliffe and Comet West-Kohoutek-Ikemura in a demonstration of
new spacecraft technologies.

The lecture will be hosted by Dr. Don Yeomans, a senior
research scientist in JPL's Solar System Dynamics Group. Yeomans
has been studying comets for nearly three decades, and has also
been active in planning space missions geared toward comet
studies. He will lead a discussion of what can be expected of
Comet Hale-Bopp as it brightens in the next several weeks.

For further information, contact the Public Information
Office at (818) 354-5011.